Statistics for defensive performance

There are a lot of Corsi-derived statistics out there, but I can't find any that measures the difference in Corsi of their opponents between their average and when they match up against the player in question.

Example: Daniel Sedin had a Corsi On of 21.09. Let's say that when he played against Rob Scuderi he only managed 13.09, this would give Scuderi a Corsi Opp of 8.00 vs Daniel Sedin. His total Corsi Opp would be the average of all the players he has been on the ice against weighted for icetime.

All the statistics required for calculating this is already being measured for use in Corsi and Qualcomp, why haven't this been put together before? I'd say it could be a good way of measuring a player's defensive performance. Of course it still doesn't account for playing style, but the guys that have bad Corsi Rel due to playing difficult minutes could be accurately measured in how good they are at containing the opposition.

Addendum:

This was something that just popped into my head last night, and after mulling it over and doing some calculations this morning I realized it was an incomplete measure of how a player affects the flow of play since the QoT wasn't accounted for.

A good measure would be the difference of expected Corsi and the Corsi of the player in question.

Expected Corsi would be: Corsi Qot - Corsi QoC. If your teammates have an average Corsi of -4 and the opposition an average Corsi of 2, the expected Corsi would be a -6.

If a player in that situation would have a Corsi of -2, it would be (-2) - (-6) = 4 point higher than expected, i.e. this player pushed the flow of play 4 points in the favour of his team when he was on the ice.

The top 30 in CorsiQoC would basically only be Nashville, Calgary, and Columbus players and would not be that interesting to look at. I'll be able to do more comprehensive studies on 2011-2012 when behindthenet.ca releases an .xls file for that season. Now it's just too much work.

There are a lot of Corsi-derived statistics out there, but I can't find any that measures the difference in Corsi of their opponents between their average and when they match up against the player in question.

Example: Daniel Sedin had a Corsi On of 21.09. Let's say that when he played against Rob Scuderi he only managed 13.09, this would give Scuderi a Corsi Opp of 8.00 vs Daniel Sedin. His total Corsi Opp would be the average of all the players he has been on the ice against weighted for icetime.

All the statistics required for calculating this is already being measured for use in Corsi and Qualcomp, why haven't this been put together before? I'd say it could be a good way of measuring a player's defensive performance. Of course it still doesn't account for playing style, but the guys that have bad Corsi Rel due to playing difficult minutes could be accurately measured in how good they are at containing the opposition.

Addendum:

This was something that just popped into my head last night, and after mulling it over and doing some calculations this morning I realized it was an incomplete measure of how a player affects the flow of play since the QoT wasn't accounted for.

A good measure would be the difference of expected Corsi and the Corsi of the player in question.

Expected Corsi would be: Corsi Qot - Corsi QoC. If your teammates have an average Corsi of -4 and the opposition an average Corsi of 2, the expected Corsi would be a -6.

If a player in that situation would have a Corsi of -2, it would be (-2) - (-6) = 4 point higher than expected, i.e. this player pushed the flow of play 4 points in the favour of his team when he was on the ice.

Corsi On - (Corsi QoT - Corsi QoC)

You also have to account for shot quality allowed on ice. (and yes I've heard all the arguments that SV% and SH% are not repeatable across the entire NHL population). I don't buy it for D men population though. They have much more impact of what goes on in front of the netminder than forwards who just add to the noise.

The last year listed (08-09), they were both playing in front of the same goaltender, yet Scuds "lucked" (sarcasm) out by having a huge SV% advantage (.031) while on ice, AND while facing tougher qual comp.

There are players that allow a lot of low quality shots (Good defensive only Dmen) and players that allow few, but high quality chances (offensive defensemen). Then you have your elite that are good at both and your scum which aren't good at anything.

You also have to account for shot quality allowed on ice. (and yes I've heard all the arguments that SV% and SH% are not repeatable across the entire NHL population). I don't buy it for D men population though. They have much more impact of what goes on in front of the netminder than forwards who just add to the noise.

The last year listed (08-09), they were both playing in front of the same goaltender, yet Scuds "lucked" (sarcasm) out by having a huge SV% advantage (.031) while on ice, AND while facing tougher qual comp.

There are players that allow a lot of low quality shots (Good defensive only Dmen) and players that allow few, but high quality chances (offensive defensemen). Then you have your elite that are good at both and your scum which aren't good at anything.

2 parts

- # of shots allowed vs expected
- SV% of goalie on ice vs expected

I agree that Corsi, adjusted for strength of teammates and opposition, and based on quality of shots allowed, not just quantity, would be as perfect a stat as you could get.

And we have everything we need to calculate this, IIRC, so what are we waiting for?

then again there is one hitch. Corsi is based on all shots directed at the net, not just SOG. Shot quality "rates" shots based on their likelihood of scoring, with a base of 1.0 being an "average" shot. tough shots are higher, easy shots are lower. what are missed shots? how do you assign them a rating? it would have to be based on a percentage chance that the missed shot could have been a legitimate shot, based on more data. also, a blocked shot would have to still count as a shot directed at the net (which is bad) but could be counted as "less of a shot" since it didn't get there (which is good). that's all well and good, but then what is it? 0.2? 0.9? somewhere in between? It would have to be somehow quantified logically.

The problem with Corsi stats against certain opponents is that you have a very small sample size.

but the aggregate is a large sample size. Yes, your final result is based on just 10 minutes against player A, 8 minutes against player B, etc... but the total is all weighted properly and based on 2000 minutes.

same thing as shot quality. don't focus on the fact that it includes "only" 12 point blank wrist shots and "only" 14 wraparound attempts and "only" 22 slap shots from the point. it's still a large sample that includes 1000+ shots in total.

In other words, I don't care what someone's Corsi was in particular against a certain player. I want to know about their season-long tendencies.

hmmm, in theory it looks ok, and it appears to identify "some" of the correct players. However, why do four clear offensive specialists get on there?

Something about QoC not being factored in properly, I imagine. Perhaps they were quite good at not getting scored on by second rate forwards, but that should almost preclude them from being compared to the guys who played against first rate forwards. Just thinking out loud.

hmmm, in theory it looks ok, and it appears to identify "some" of the correct players. However, why do four clear offensive specialists get on there?

Something about QoC not being factored in properly, I imagine. Perhaps they were quite good at not getting scored on by second rate forwards, but that should almost preclude them from being compared to the guys who played against first rate forwards. Just thinking out loud.

Right on... i was starting from stratch, so i'm sure there are a bunch of modifications that can be made to improve the formula.

Those offensive specialists were actually forced to play in their zone and did pretty well.
When i have access to my spreadsheet (work computer) I'll post their ranking in each category to show how they ranked...
conversely if there is another specific dman you were expecting to be ranked, post, i;ll post their numbers to show how they placed...

Just a question about this, where exactly are you getting the evidence in how much each stat is weighed?

The goal was to select only statistical categories which reflected the defensive part the the game. So thats difficult in itself.

But after selecting the handful of categories above, I.took poll and tried to determine which categories were relatively considered more important.

So that's the subjective part. In an earlier version, I ran the numbers as all equal, but there was obvious difference in importance of some of the stats and a significant effect of superior team play.... But I.did love the look of the shorthanded results of the list...

Quote:

Quality of competition Corsi quality of Comp Relative Corsi ... ( i don't know the difference between relative and regular) (Goals against while Off/60) - (Goals against while On/60) Blocked shots PDO - Team shooting % + team save % while player is On the ice Zone start % Difference in Zone finish % vs zone start %

Right on... i was starting from stratch, so i'm sure there are a bunch of modifications that can be made to improve the formula.

Those offensive specialists were actually forced to play in their zone and did pretty well.
When i have access to my spreadsheet (work computer) I'll post their ranking in each category to show how they ranked...
conversely if there is another specific dman you were expecting to be ranked, post, i;ll post their numbers to show how they placed...

Robidas and Mitchell, for starters.

Quote:

Originally Posted by begbeee

I'm not interested in numbers much, but how can you explain Visnovsky as TOP5 defensive defensman?

it looks like the factors chosen, although they all make sense, were just not weighted "properly". It was a subjective exercise and it appeared to work, to some degree.

the CORSI part is probably a major flaw. Just like people correctly say "you can't use +/- as an indication of defensive ability because goals for are half the equation", the same is true about CORSI, only with shots instead of goals. So these offensive specialists are getting shots to the other team's net and advancing the puck, and helping their corsi, but not really proving themselves defensively in the process.

also, I see that zone finishes minus zone starts is a factor. I think this is a mistake. If players like Matt Carle and Visnovsky are getting a defensive zone start, it won't be against the best players. therefore, they will defend the zone, and advance the puck for the next faceoff. Doesn't prove they're that good defensively. I would use raw zone starts. I know that doesn't say what happened on that shift, BUT the fact that their coach is using them in that situation on a regular basis says much more, IMO.

I'm not sure PDO is important to use. It's very random. It's true that some players will "earn" better PDOs by limiting shot quality against and creating higher quality scoring chances, but that isn't extremely common, and PDO is still a reflection of both ends of the ice, like CORSI.

DL44 - It sounds like you have these numbers all in a spreadsheet. If you do, try this subjective weighting and get back to me with a top-20:

=10*(G5)+6*(ZS)+4*(M5)+3*(AB5)

basically, who's getting the big minutes in the defensive zone against the best players, and to a lesser extent, who is still helping out on the CORSI side (keeping corsi in there does introduce a little bit of offensive "noise" but only about 6.5% of the total)

also, I see that zone finishes minus zone starts is a factor. I think this is a mistake. If players like Matt Carle and Visnovsky are getting a defensive zone start, it won't be against the best players. therefore, they will defend the zone, and advance the puck for the next faceoff.

I'm not sure why you're assuming this. Visnovsky and Lydman faced easily the toughest quality of competition on Anaheim in 2010-11 and absolutely killed it. Visnovsky might not have a reputation as a strong defensive player who matches up against top lines but that's how he was used that season.

I'm not sure why you're assuming this. Visnovsky and Lydman faced easily the toughest quality of competition on Anaheim in 2010-11 and absolutely killed it. Visnovsky might not have a reputation as a strong defensive player who matches up against top lines but that's how he was used that season.

Thanks for the correction. I think we're getting to the bottom of it.

Lydman is the one with the exemplary defensive reputation, going back almost a decade now. If Visnovsky was his partner, then to some degree he was carried to a better defensive rating. Of course, like all pairings, they weren't joined at the hip, and in the numbers you can see, Visnovsky got some more offensive shifts against lesser competition and boosted his corsi, so he'd look better by the metrics DL44 is using.

usually he has faced the weaker competition based on qualcomp in 08, 09, 10, and 12, but you're right, he did get tougher shifts in 2011.

In terms of what i did for rankings.. for each category the players were ranked 1 thru - 173. It was thos rankings i used in the formula... not the actual raw numbers.

Oh, I see.

I'm not sure how that would affect it, but it would certainly insulate exceptionally good and bad players from looking like they deserve, and it would also make a player not too much above average who happens to be 24th out of 173 and only 10% better than the guy in 140th, look a lot better than they deserve.

These numbers should probably be averaged, then each factor for each player can be expressed as a percentage of that average.

I'm not sure how that would affect it, but it would certainly insulate exceptionally good and bad players from looking like they deserve, and it would also make a player not too much above average who happens to be 24th out of 173 and only 10% better than the guy in 140th, look a lot better than they deserve.

These numbers should probably be averaged, then each factor for each player can be expressed as a percentage of that average.

thought about that..
that's where sample size comes in a bit - over a range of 173 players, there really isn't much tiering of players... its a pretty gradual progression.

And if there was to be tiering in any particular category where a player jumps up as an outlier vs the comp, its effects are squashed out with the multiple categories.

So i was going to start with a new spreadsheet based on the 2011 - 2012 season...

What do we suppose the categories should be and the make up of the formula we implement?

thought about that..
that's where sample size comes in a bit - over a range of 173 players, there really isn't much tiering of players... its a pretty gradual progression.

And if there was to be tiering in any particular category where a player jumps up as an outlier vs the comp, its effects are squashed out with the multiple categories.

So i was going to start with a new spreadsheet based on the 2011 - 2012 season...

What do we suppose the categories should be and the make up of the formula we implement?

Your guess is as good as mine. you started with something, I made what appeared to be improvements, but until I see the results I don't even know if they really are. In any case it's probably just subjective weighting of objective numbers. The heavy stats guys tend to have ways to logically lay out how different factors should be weighted.